Since Mono-Green decks generally take advantage of a lot of creatures, this allows you to constantly scry cards from your deck to ensure that your next draw will never be a bad one
While it isnt mandatory to play the color of your Character Booster, I expect almost all players to do so
Even if Roon isnt your commander, as long as your blink deck has access to blue and/or green plus a blink spell that can target opposing creatures, this can be a nasty little trick that your opponent probably wont see coming the first time, and one theyll have to consider playing around thereafter
The frames for the miracle cards from the Avacyn Restored set, that had a special border that appears as if the art is bathed in light and the hybrid cards from the Ravnica, City of Guilds set are examples of different card frames that I would file in this category: The miracle card frame is beautiful, but the card wouldnt lose much without it
The first category is commonly seen in vintage cubes